1. Field of the Invention
The present invention relates to an infrared convection paint-baking oven that uses infrared lamps to directly apply heat to the painted part and uses air from a blower to supply convection to the infrared heat and evenly distribute the heat throughout the oven interior to evenly cure paint finishes on parts arranged therein.
The present invention further relates to a method of efficiently paint baking automotive parts arranged on a conveyer in an oven that reduces the time necessary to cure such parts over prior art ovens and processes.
The present invention further relates to an infrared convection paint baking oven wherein the infrared light assemblies are arranged such that they are diagonally opposed to each other and the articles to be cured, so that the heat provided by such light assemblies is circulated through the oven interior and the automotive parts by convection air currents, thereby resulting in an even temperature throughout the curing process and a extended lamp life due to the circulation of air around the light assemblies.
2. Detailed Description of the Related Art
Josefsson et al., U.S. Pat. No. 5,235,757 discloses a convection air holding zone in a camel back paint oven that utilizes turbulent ejector air flow along paths parallel to the path of travel of the article being baked in a paint bake oven. Air recirculation means are provided within the convection air holding zone which filters dirt particles from the air and a heat source is applied to the air to compensate for temperature loss due to heat exchange with the article and oven walls. Maintaining a turbulent air flow over the article being baked in the convection air hold zone helps insure an even temperature throughout the zone, thereby enabling a more consistent paint finish on the article. Dark radiation panels are used to supply heat to the oven. There is no disclosure of using infrared lamp assemblies in combination with convection air currents to maintain the heat in the oven at a consistent temperature.
Josefsson et al., U.S. Pat. No. 5,323,485 discloses a paint baking oven having a bring up zone utilizing short and medium wave infrared lamps to raise the component temperature up to a desired level. Once within the paint baking oven, a computer activates the requisite number of infrared lamps at the proper intensity to achieve the desired component temperature. While the infrared lamps are activated, inlet air is directed over the lamps to prevent them from overheating. The invention allows for smoother car finishes by preventing bubbling, pops, and raises the component temperature more quickly than conventional dark radiation panels. Josefsson et al specifically state that the heating means generally comprise a plurality of centrally directed infrared lamps extending from a frame member which selectively projects radiation onto the component as it passes through the leading end of the bring up zone. The bring up zone further includes an air inlet system for bringing air into the interior of the bring up zone. The air serves to cool the infrared lamps which are susceptible to overheating. Once the inlet air approaches the entrance end of the bring up zone, it is recirculated back into the bring up zone by a draft of air introduced by a blower. The air passes through a filter to remove solvents and dust and is then reintroduced into the bring up zone. There is no disclosure of arranging the infrared lamps in a diagonally opposed manner and neither is there a disclosure of using infrared lamps to provide heat throughout the entire length of the paint bake oven and neither is there any disclosure of using recirculated air to create a convection heat throughout out the entire length of the paint bake oven to provide and even temperature throughout the length of the paint bake oven.
Habaki et al., U.S. Pat. No. 5,155,335 discloses an oven for baking a powdered coating material to an object. The oven has an inlet air shield chamber connected to the inlet side of a horizontal heating chamber. The inlet air shield chamber is provided therein with a radiation heat source which heats the object and the layer of coating powder to a temperature substantially equal to the baking temperature before the object enters into a horizontal heating chamber. The horizontal heating chamber is provided with a source of heated air from a gas fired hot air generator.
There is no disclosure of using infrared heat lamps arranged in a diagonally opposed manner together with recirculated air to provide a convection air flow to maintain a consistent baking temperature throughout the entire length of a paint baking oven.
Nelson et al., U.S. Pat. No. 4,908,231 discloses a process and apparatus for heat treating a coating applied to an automobile body. The process includes the steps of radiant heating of a coating prior to convection heating.
The present invention is directed to a process and apparatus for applying radiant heat as well as convention heating simultaneously to cure an article to be coated.
Emch, U.S. Pat. No. 6,231,932 discloses a process for drying or curing top coatings and multi-component composite coatings applied to surfaces of metal or polymeric substrates which include applying infrared radiation and warm low velocity air simultaneously to the coating for a period for at least about 30 seconds and increasing the substrate temperature at a predetermined rate to achieve a specified peak temperature. Infrared radiation and hot air are applied simultaneously to the coating for at least about three minutes and the substrate temperature is increased at a predetermined amount to achieve a specified peak temperature, such that a dried and/or cured coating is formed upon the surface of the substrate. The specified peak temperature for exposing the top coating is 10° C. to 40° C. for a period of about 30 seconds and then applying the infrared and warm air at a volume not to exceed 4 meters per second, and the temperature should not exceed 25° C. to 50° C., and then applying infrared and hot air for at least 30 seconds so that the temperature of the metal substrate is increased to a range of about 65° C. to 140° C. to dry the top coat.
The present invention is directed to a paint bake oven that uses infrared lamp assemblies in a specific arrangement to heat the substrate of an article to be cured to about 265° C. for about 2 minutes, and then uses infrared radiation and convention air currents to maintain the temperature for an additional 8 to about 20 minutes, depending upon the finish being cured. The temperature ranges and the times used are outside the ranges contemplated by Emch '932.
Emch, U.S. Pat. No. 6,133,764 discloses a process of drying a liquid electro deposited coating composition applied to a metal substrate. Infrared radiation and warm air are applied simultaneously to the electrodeposited coating composition for a period of at least about 1 minute and the velocity of air at the surface of the electro-deposited coating composition for a period of about 1 minute, the velocity of the air at the surface of the electro-deposited coating being less than about 4 meters per second. The temperature of the metal is raised in a controlled manner to about 35° C. to 140° C. Infrared radiation and hot air are then applied for a period of at least 2 minutes to achieve a temperature of the substrate of about 160° C. to about 215° C. such that the dried electrodeposited coating is formed upon the surface of the metal substrate.
The present invention is directed to a paint bake oven that uses infrared lamp assemblies in a specific arrangement to heat the substrate of an article to be cured to about 265° C. for about 2 minutes, and then uses infrared radiation and convention air currents to maintain the temperature for an additional 8 to about 20 minutes, depending upon the finish being cured. The temperature ranges and the times used are outside the ranges contemplated by Emch '764.